PIA19716: Alice Solar Occultation

Alice Solar Occultation


This figure shows how the Alice instrument count rate changed over time during the sunset and sunrise observations. The count rate is largest when the line of sight to the sun is outside of the atmosphere at the start and end times. Molecular nitrogen (N2) starts absorbing sunlight in the upper reaches of Pluto's atmosphere, decreasing as the spacecraft approaches the planet's shadow. As the occultation progresses, atmospheric methane and hydrocarbons can also absorb the sunlight and further decrease the count rate. When the spacecraft is totally in Pluto's shadow the count rate goes to zero. As the spacecraft emerges from Pluto's shadow into sunrise, the process is reversed. By plotting the observed count rate in the reverse time direction, it is seen that the atmospheres on opposite sides of Pluto are nearly identical.

Background Info:

The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA's Science Mission Directorate. The Southwest Research Institute, based in San Antonio, leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.

Cataloging Keywords:

Name Value Additional Values
Target Pluto
System Pluto Kuiper Belt
Target Type Dwarf Planet KBO
Mission New Horizons
Instrument Host New Horizons Cassini Orbiter
Host Type Flyby Spacecraft
Instrument Alice Ultravilet Spectrometer
Extra Keywords Atmosphere, Color, Methane, Occultation, Shadow
Acquisition Date
Release Date 2015-07-17
Date in Caption
Image Credit NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Source photojournal.jpl.nasa.gov/catalog/PIA19716
Identifier PIA19716